Effective production of liquid/wax fuels from polyethylene plastics using Ru/Al2O3 catalysts†

Abstract

Hydrogenolysis provides a promising pathway for converting polyolefin plastics into valuable liquid and wax fuels. This process involves dehydrogenation, C–C bond cleavage, and hydrogenation at the active metal sites of the catalyst. Controlling the nature of these metal sites is crucial to optimize overall reaction activity. In this study, Ru catalysts supported on nanosheet-assembled Al₂O₃ (NA-Al₂O₃) were used for the hydrogenolysis of polyethylene (PE). Unlike commercial Al₂O₃, NA-Al₂O₃ promotes Ru–Al bond formation, leading to stronger metal–support interactions. Under identical Ru loadings, these enhanced interactions resulted in higher Ru dispersion and smaller Ru species on the NA-Al₂O₃ surface. To investigate the effect of Ru loading, a series of catalysts (xRu/NA-Al₂O₃, x = 0.5, 1, 5, and 8 wt% Ru) was synthesized, revealing that Ru particle size and electronic properties varied with Ru loading. Among them, the 1Ru/NA-Al₂O₃ catalyst, featuring optimally sized Ru species (∼0.8 nm) and a tailored electronic structure, demonstrated the highest efficiency in PE hydrogenolysis by effectively suppressing successive C–C bond cleavage. This catalyst achieved an outstanding PE conversion rate of 1.15 × 10³ g_{converted PE} g_Ru⁻¹ h⁻¹ and a liquid/wax production rate of 9.23 x 10² g_liquid/wax g_Ru⁻¹ h⁻¹, highlighting its superior performance in catalytic PE hydrogenolysis.